The invention relates to a filling apparatus for filling cavities in a rotary press comprising a filling material reservoir and a filling chamber that is connected to the filling material reservoir and has a filling opening from which the filling material can pass into the cavities of the rotary press.
By means of a filling apparatus, the cavities of a rotary press are filled, metered, and/or pre-compressed with the pressing material to be pressed by the punch of the rotary press. The upper and bottom punches of the rotary press interact in the cavities to press pellets. The quality of the produced pellets depends significantly on the quality of cavity filling. Features that are examined when determining the quality of the produced pellets are, for example, the pellet weight, breaking strength, density distribution and amount of active ingredient. Reproducible pellet quality is an important manufacturing characteristic according to the pharmacopoeia and requires a reproducible cavity filling quality. The cavity filling quality can, for example, be understood as the degree of fluctuation of the fill amounts and/or the density distribution of the pressing material within a single cavity and/or the integrity of the pressing material. For example, a small fluctuation range of the fill amounts can ensure an even weight of all the produced pellets.
The filling apparatuses must ensure that the cavity filling quality is retained even with the high performance of today's rotary presses. Known filling apparatuses are based on different concepts such as chamber filling shoes and single or multi-chamber filling systems. Frequently, stirrer blade wheels are rotatably driven in the filling chambers of the filling apparatuses. Stirrer blade wheels are used in particular for high performance rotary presses. Stirrer blades with different numbers and shapes of stirrer blades are known. Pressing material is continuously transported by the rotary blades to the cavities so that, even at high speeds, the rotary press ensures the availability of a sufficient amount of pressing material to fill the cavities. Moreover, the stirrer blades loosen the pressing material which positively influences the flowability. This allows a consistent cavity filling quality to be ensured even at a high tableting output.
The effect of the stirrer blades of the stirrer blade wheels on the cavity filling quality is dependent inter alia on the pressing material to be pressed. The stirrer blades can have a significant influence on the transported amount of pressing material, and/or on the extent to which bridge formation is prevented, and/or loosening. In addition, by selecting appropriate stirrer blades, disadvantageous effects can be prevented such as a decomposition or heating of the pressing material. It is, however, difficult to find a stirrer blade configuration that realizes all of the various goals. For example, a certain stirrer blade configuration can ensure an effective transportation of the pressing material to the cavities. However, it does not offer satisfactory loosening of the pressing material at all times. Conversely, a stirrer blade configuration that, for example, ensures effective loosening of the pressing material may not ensure satisfactory transportation of the pressing material to the cavities. A conflict between goals accordingly exists in practice.
Based on the presented prior art, the object of the invention is therefore to provide a filling apparatus of the aforementioned type which also satisfactorily meets various requirements with regard to cavity filling.